The present invention relates to an erector for holding a leaf-flap in various opening settings relative to its frame, in particular for holding a motor-car hood or bonnet.
A known erector is described in DE 42 39 172 C1, in which the erector is drawn apart, by attachment of its ends to the frame or to the leaf-flap, as the leaf-flap is opened, and is collapsed again as the leaf-flap is closed. Due to the purely fluidic flow regulation of the embodiment exhibiting two non-return valves and a step valve, there is no occurrence of either disturbing operating noises or measurable wear. The flow regulator is also already distinguished by a relatively simple configuration having a small number of movable parts.
An object of the present invention is to provide a substantially improved erector which has a technically simplified flow regulator in terms of a reduction in movable parts.
The foregoing object has been achieved in accordance with the present invention by providing an erector comprising a continuously length-variable dynamic unit operatively supported with respect to the leaf-flap and the frame and having a hollow cylinder and a piston movable via a piston rod and slidably guided in the hollow cylinder to divide an interior space of the hollow cylinder into two pressure-medium chambers which are overflow-connected with each other. A flow regulator is operatively interposed between the two chambers and has a direction-reversible through-flow depending upon an advancement direction of the piston. The flow regulator comprises a flow-duct system having two valves pushed open by a pressure-medium column and respectively operatively arranged at an associated overflow duct such that the overflow ducts are capable of being shut off against through-flow in one direction by the valve associated therewith one of the two valves being a control valve configured a step valve and to flow-block the associated overflow duct in both directions when the control valve is closed. The flow regulator has a push-open position constituting a pass-through setting into which it is moved under pressurization by the pressure-medium column flowing through an associated control duct, against a return force in which it is maintained up to a pressure level of the pressure-medium which is significantly lower than the control pressure of the control valve which comprises a differential piston axially displaceable against a spring load, whereby control pressure of the pressure- medium acts upon a first piston surface of the differential piston and whereby the pressure-medium which is in force in the pass-through setting acts upon a second piston surface of the differential piston which is larger than the first piston surface.
In the case of motor-car hoods or other swivel-up vehicle parts, on one hand, it is generally sufficient if a locking effect is achieved in one directional sense only. Minimal push-open forces can herein be provided for the one-way valve disposed in the overflow duct, so that restraint is not detectable. In the event of opposite-directed overflow, on the other hand, the control valve, which is determinant for the arresting locking forces, is pushed open. Excessive push-open forces are also in this case unnecessary, owing to the pressure-equalization via the equalization duct.
Preferably, the erector exhibits a dynamic unit acting as a relief spring, which can be, for example, a pneumatic spring, this being particularly advantageous for weight reasons.
A particularly compact configuration of the dynamic unit herein becomes possible if the pressure-medium in the pressure-medium chambers is kept by way of a spring store under an elevated working pressure.
Advantageously, the flow regulator can be integrated in a known manner into the piston of the dynamic unit, with a path-optimized duct system being provided.